functional anatomy spine

Nucleus Pulposus

Acts like a ball bearing and provides relative motion of two adjacent vertebral bodies by shifting in position or changing shape

Intervertebral Disc

Ampiarthrodial Joint No joint capsule Healthy Intervertebral Discs in an adult account for approximately 1/4 of the height of the spine Component parts Nucleus Pulposus Annulous Fibrous

curvatures of the vertebral column

Anterior-Posterior Curvatures Kyphotic Curves Anterior - Concave Posterior - Convex Thoracic and sacral Lordotic Curves (does not exist in fetal position) Anterior - Convex Posterior - Concave Cervical (not until child raises its head) and lumbar not until child stands)

Parts of vetebrae

Body Vertebral arch Vertebral foramen Vertebral canal Pedicles Vertebral processes Spinous process (1) Transverse processes (2) Articular processes (4)

Parts of a typical vertebrae

Body - anterior Vertebral arch - posterior Vertebral foramen Vertebral canal Pedicles Vertebral processes Spinous process (1) Transverse processes (2) Articular processes (4)

Loads on the Spine

Body weight Tension in the spinal ligaments Tension in surrounding muscles Intra-abdominal Pressure Any applied external loads

forces acting on the spine

Body weight, the weight of an load held in the hands, and tension in the surrounding ligaments and muscles all contribute to spinal compression

Osteological Factors

Cortical bone Forms a thin outer coating of the vertebra to protect and retain the cancelleous bone Cancelleous Bone Forms trabecular patterns which fill the vertebra

7 Cervical Vertebrae

Distinctive feature: Transverse foramina Bifid spinous processes Vertebra prominens (C7) Superior articular facets face UP

4 Coccygeal Vertebrae

Fuse into a single Triangular Bone called the coccyx Tailbone No weightbearing function Attachment point for muscles and ligament

5 Sacral Vertebrae

Fuse into one bone call the Sacrum Transmits weight from spine to pelvis 4 pairs of foramina Sacral canal

12 Thoracic Vertebrae

Heart-shaped bodies Spinous processes slant inferiorly Superior articular facets face REARWARD

Low Back Pain

In the absence of contraction of the surrounding musculature, buckling of the lumbar spine occurs under compressive loads as small as 4 N

Structure of the Spine

Lordosis - exaggerated lumbar curve Kyphosis - exaggerated thoracic curve Scoliosis - lateral spinal curvature

Stress Fracture

Most common type of vertebral fracture is in pars interarticularis, the region between the superior and inferior articular facets Spondylolysis Spondylolisthesis Spondylolysis and spondylolisthesis don't tend to heal with time

upright standing, compression on the lumbar spine increases with:

Sitting More with spinal flexion Even more with a slouched sitting position

5 Lumbar Vertebrae

Sturdy laminae and transverse processes Kidney-shaped bodies Superior articular facets face INWARD

Annulous Fibrous

The fibrous capsule which surrounds and retains the pulpy nucleus

Vertebral Column functions

Transmit force from the upper extremities to the pelvic girdle Assist in attenuation of impact shock Provide relative motions between pelvic girdle and shoulder girdle The spine enables motion in all 3 planes, yet still functions as a bony protector of the spinal cord

Motion Segment

Two adjacent vertebrae and the soft tissues between them Considered to be the functional unit of the spine Each motion segment contains three joints The vertebral bodies separated by the intervertebral disc form a symphysis type of ampiarthrosis The right and left facet joints between the superior and inferior articular processes are diarthroses of the gliding type

The spine consists of a

curved stack of 33 vertebrae divided into 5 regions 7 Cervical Vertebrae 12 Thoracic Vertebrae 5 Lumbar Vertebrae 5 fused Sacral Vertebrae 4 small, fused Coccygeal Vertebrae

Lumbar hyperextension

produces compressive loads at the facet joints.

Atlas & Axis

the 1st and 2nd cervical vertebra

During erect standing

the total body center of gravity (COG) is anterior to the spinal column This places the spine under a constant forward bending moment To maintain body position: This torque must be counteracted by tension in the back extensor muscles